Disposable diapers have become an accepted substitute for cloth diapers and several different constructions have achieved significant market penetration. Many of the disposable diaper configurations are rectangular and flat, and comprise sheets which are fitted to a baby from a flat state. In some instances the diaper may incorporate a geometrical folding for shape. Two very serious drawbacks with prior art disposable diapers have been the problems of fit, both around the legs and around the waist of the infant, as well as the strength of the diaper in the area where it is secured about the infant.
In solving these problems with disposable diapers, because of the nature of the product, the economics are of primary importance. The problem of fit is easily and simply solved merely by making marginal portions of the diaper elastic to improve the conformability about the legs of the infant and/or the waist of the infant. The problems of reinforcing the edge or corners of the diaper to make them stronger in their securement areas is easily and relatively simply solved by placing more layers of material in those areas. However, each of these operations will increase the complexity of the manufacture of the diaper and increase the cost of raw materials used in the diaper and hence substantially increase the ultimate cost of the diaper.
For enhanced fit, in the recent past disposable diapers with contractable side flaps which gather the side margins of a diaper have been introduced into the marketplace. Such diapers are similar to conventional moisture-impermeable panties and tend to improve the fit of the diaper about the legs of the wearer, yet are costly to manufacture. A diaper of this general type is described in U.S. Pat. No. 3,860,003.
There are also a number of patents which disclose means for making the waist band of disposable diapers elastic to improve the fit of the diaper about the waist of the wearer, for example, as shown and described in U.S. Pat. No. 3,995,637 and 3,995,640.
Also, various methods for incorporating elastic members in garments to make portions of the garments stretchable are well known in the art. Such methods include the use of heat-shrinkable or heat-recoverable film ribbons which are incorporated into the garments while in a non-elastic state and then treated with heat to provide the ribbons with elastic properties or to accentuate the elastic properties already present in the ribbons. Such techniques are generally described in U.S. Pat. Nos. 3,245,407 and 3,639,917.
Disposable diapers originally were secured with pins, but in recent times have been secured with pressure-sensitive adhesive tape fasteners or tabs. In both instances it is primarily the corners of the diapers which take the stress in securing the diaper to an infant and continue to absorb stress during the infant's active periods. The adhesive tabs are normally attached at one end thereof at the side margins of the diaper and are secured to the relatively thin backing sheet of the diaper. Since the stress is greatest in these areas, it has been known to reinforce these areas by various techniques, for example, by the use of a scrim adhered to the area, such as is disclosed in U.S. Pat. No. 3,867,940, or by thickening the backing sheet in the area of attachment as illustrated in U.S. Pat. No. 3,783,871. In either case registry problems are encountered during high-speed manufacture.